The objective of this research is to elucidate radiation damage processes at the molecular level. An experimental capability has been developed at this laboratory for stabilizing and identifying primary radiation products. The primary products are stabilized by maintaining the irradiated sample at 4.2 degrees K or lower. The products are identified using ENDOR (electron-nuclear double resonance) spectroscopy. In the proposed research the principal objective will be to add a kinetic dimension to these studies. A linear accelerator (newly available at RPMI) can produce the requisite radiation damage in a fraction of a second. With the irradiated sample maintained at a predetermined temperature, magnetic resonance methods will be used to monitor the transformation of primary radiation products which occurs when secondary processes such as electron transfer and proton transfer are allowed to operate. The activation energy of these secondary processes will be determined. Of particular interest will be to learn the mechanism by which primary radiation-induced oxidations and reductions lead eventually to chain breaks in irradiated DNA molecules.